Injection locking techniques have been used in a number of laser systems. This technique is of particular interest when a low power laser with desirable frequency properties (the master) is used to impose its frequency and mode structure onto a higher power laser (the slave) whose spectral properties would otherwise not be as good.
This latter result is achieved by injecting the output of the master laser into the cavity of the slave laser. As the frequency of the master laser approaches one of the axial mode frequencies of the slave laser, light from the master laser is regeneratively amplified to higher intensities, eventually saturating the gain in the slave laser to such an extent that the original free-running mode of the slave laser is extinguished. Within this locking-range, the output of the slave laser is frequency locked to the output frequency of the master laser. Injection locking offers the advantage of single-frequency operation of a high power laser without the use of etalons or other intracavity elements that reduce the efficiency and output power of the laser.
The term injection locking is most often used to refer to systems wherein a the output from a CW master laser is injected into a CW slave laser. This should be contrasted to the situation where the output of a CW master laser is injected into a pulsed slave laser which is more appropriately and often called injection seeding. Injection seeding is theoretically less stringent since it is easier to force a mode of operation on an intermittent slave. The requirements for imposing a given frequency and mode structure onto a circulating beam of energy in a CW slave laser are much greater.
Injection locking techniques have been successfully used with ion lasers, dye lasers and diode lasers. Efforts to extend this approach to solid state lasers have principally been limited to systems where the master and slave laser operate at roughly the same power level. The resulting output is a summation of the two output powers. This approach is often referred to as coherent summation or chaining. These prior art systems are very sensitive and not particularly stable. More importantly, the output of the slave laser was of the same order of magnitude as the master laser. Therefore, it would be desirable to provide an injection locking system for solid state lasers which is highly stable and can be used to generate high powers.
Accordingly, it is an object of the subject invention to provide a new and improved solid state injection locked laser system.
It is a further object of the subject invention to provide an injection locked laser system for continuous wave lasers.
It is another object of the subject invention to provide an injection locked laser system for a high power solid state slave laser.
It is still a further object of the subject invention to provide a laser system where a master laser is used to injection lock a solid state ring laser.
It is still another object of the subject invention to provide an injection locked laser system wherein the output power of the slave laser is at least one order of magnitude higher than the output power of the master laser.
It is still a further object of the subject invention to provide an actively stabilized injection locked laser system.